High-frequency radiant energy absorbing device



June 1949. D. E. SUNSTEIN HIGH-FREQUENCY RADIANT ENERGY ABSORBING DEVICE Filed April 28, 1944 I N V EN TOR. Jczgzd Z f amsfezkz/ W7 Patented June 28, 1949 HIGH-FREQUENCY RADIANT ENERGY ABSORBING DEVICE David E. Sunstein, Elkins Park, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application April 28, 1944, Serial No. 533,233

3 Claims.

I The present invention relates to a device for absorbing ultra high frequency radiant energy so that ultra high frequency transmitting equipment may be adjusted and calibrated as though Operating into free space.

I-Ieretofore, in connection with radio frequency transmitters, it has been common to utilize a dummy antenna in place of the radiating antenna during those times when the radio transmitter is to be adjusted or calibrated. Dummy antenna devices operate satisfactorily in the lower frequency bands, but a comparable device is not obtainable for use with ultra high frequency radio transmitting equipment. In the manufacture of ultra high frequency radio transmitters, it is necessary to test, calibrate, and adjust the transmitters and, because of the critical nature of the circuits and the apparatus, it is necessary to connect the sources of ultra high frequency energy to the radiator or antenna device which is actually used with the apparatus. In order that the radiation from such radiator might not interfere with other equipment in the place where the transmitter is being tested, it is desired to provide a device which will substantially completely absorb the radiated ultra high frequency energy. In accordance with the present invention this is accomplished by positioning a horn adjacent the radiator with its axis substantially in alignment with the direction of the 1,

radiated high frequency energy so that transmission into free space is simulated.

It, therefore, is an object of the present invention to provide a method of and apparatus for simulating transmission into free space by ultra high frequency radiant energy apparatus.

It is another object of the present invention to provide a device for absorbing substantially completely the energy radiated by an ultra high frequency radiator.

Other and further objects of the present invention subsequently will become apparent by reference to the following descriptions taken in connection with the accompanying drawing, wherein Figure 1 is a schematic cross-sectional representation of an ultra high frequency radiator and an absorbing device embodying the present invention; and

Figure 2 is a schematic perspective representation of another form of radiator and absorbing device embodying the present invention; and

Figure 3 is a schematic cross-sectional representation of another form of the invention.

In Figure 1 there is shown a coaxial cable or transmission line having an outer conductor It and an inner conductor ll terminating in a dipole antenna l2 placed at the focal point of a reflector which, in the form illustrated, is a paraboloid of revolution. Aligned with the axis of the paraboloid l3 and with the direction of the radiated ultra high frequency energy is an absorbing device It which may be in the form of a pyramid of four sides having a base dimension equal to or larger than the over-all diameter of the paraboloid [3. The pyramidal absorbing device I4 has dimensions large compared to the wave length of the radiated energy.

It has been found convenient to utilize a pyramidal absorber of four sides since such device may be made collapsible to facilitate portability. For example, in one instance it has been found satisfactory with a wave length of one and one-fourth inches to utilize a hollow metallic pyramid of approximately square cross section with a base dimension of about twenty-four inches and an altitude of about thirty-six inches. In the example referred to, the inner surface of the absorbing device was smooth and coated with a highly conductive layer of metal, such as silver, and yet 98 per cent of the incident energy was absorbed. With an unpolished surface or one coated with a resistive material, an even greater absorption may be obtained.

In Figure 2 there is shown another transmission line comprising an outer conductor !5 and an inner conductor is connected to a dipole radiating device ll located at the focal point of a cylindrical paraboloid Hi. If desired, the paraboloid l8 may have closed top and bottom sides. The parabolic reflector, therefore, has a predetermined flare so as to transmit a rather flat beam. In order to absorb such beam, an absorbing device It is provided which is flared in the same plane as that of the radiator or reflector l8. Therefore, the absorbing device I9 may have two triangular sides and an open base or mouth so that the dimensions are large compared to the wave length of the radiated energy. The absorbing device [9 is arranged to have its axis in substantial alignment with the direction of the radiated energy beam, and the mouth of the device preferably is of equal or greater dimensions than the mouth or opening of the reflector is of the radiating assembly.

From the example shown in Figure 2, it will be appreciated that the absorbing device such as M might also be a conical pyramid having dimensions of the order previously expressed and being arranged so that its axis is in substantial alignment with the direction of the radiant energy beam.

The arrangement shown in Figure 3 illustrates the use of a parabolic reflector 2| energized with ultra high frequency energy by means of a coaxial line having an outer conductor 22 and an inner conductor 23 connected to a dipole antenna 24. A horn 25 which has been shown conical is connected to a circular Wave guide or coaxial transmission line 26. Mounted within the line 26 is an absorption member 21 having a tapered portion 28 looking toward the apex end of the horn 25. The absorption device 21 preferably comprises a ceramic member containing finely divided resistive material such as graphite, carbon black or silicon carbide. Energy collected by the horn 25 is fed to the guide or transmission line 26 so that the incident energy impinges upon the member 27. The taper portion 28 of the member 21 is so arranged as to prevent any substantial reflection of energy back along the line or guide 26. The energy entering the member 21 is absorbed and converted into another form such as heat. It, therefore, will be appreciated that the arrangements shown in Figures 1 and .2 might be provided with similar absorption devices to insure complete absorption and dissipation of incident energy in the horn.

While for the purpose of illustrating and describing the present invention, certain specific embodiments and representations have been shown, it is to be understood that the invention is not to be limited thereby, since obviously, such variations may be made therein as are commensurate with the spirit and scope of the invention as defined in the appended claims.

The. present invention is hereby claimed as follows:

1. Apparatus for simulating the transmission of ultra high frequency energy into free space, comprising a radiation device to which said energy may be supplied, and a horn having an open mouth arranged to receive energy radiated from said device and adapted to absorb substantially all of said energy, said horn tapering from adimension considerably greater than cut-01f to a dimension less then cut-ofi for the frequency range of said energy.

2. Apparatus for simulating the transmission of ultra high frequency energy into free space, comprising a directional radiation device to which said energy may be supplied, said device having a flare in a direction transversely of the direction of radiation, and means for absorbing substantially all of the energy radiated by said device, said means consisting of a horn composed of electrical conducting material and having an open mouth positioned to receive said radiated energy, said horn being flared in the same plane as said radiation device, said horn tapering from a dimension considerably greater than cut-off to a dimension less then cut-off for the frequency range of said energy.

3. Apparatus for simulating the transmission of ultra-high frequency energy into free space, comprising a radiation device to which said energy may be supplied, and a horn having an open mouth arranged to receive energy radiated from said device and adapted to absorb substantially all of said energy, said horn tapering from a dimension considerably greater than onehalf the wave length of the radiated energy to a dimension less than one-half said wave length, said dimensions being measured in a transverse direction to the electric lines of force of the field of said radiated energy.

DAVID E. SUNSTEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,923,916 Darbord Aug. 22, 1933 2,054,896 Dallenbach Sept. 22, 1936 2,094,602 Kassner Oct. 5, 1937 2,151,118 King et al Mar. 21, 1939 2,210,415 Kellogg Aug. 6, 1940 2,245,669 Hollmann June 17, 19.41 2,273,547 Von Radinger Feb. 17, 1942 2,293,181 Terman Aug. 18 1942 2,293,839 Linder Aug. 25, 1942 2,307,012 Barrow Jan. 5, 1943 2,398,606 Wang Apr. 16,1946 

